Multilayer optical fiber sheet, optical fiber sheet fabricating method, and optical fiber sheet

ABSTRACT

In order to avoid a frequent multiple crossing in an optical fiber in a sheet and attach the optical connector near a marginal end of the sheet while maintaining a sufficient extra length and more extra length for attaching the optical fibers, in the optical fiber sheet  6 , an optical fiber  5  as an extra length section in the optical fiber path is disposed on three-layer wiring planes which are formed by attaching four sheets  1, 2, 3 , and  4 . Notched sections  2   a  and  3   a  are formed in the intermediate layers  2  and  3 . The optical fiber  5  communicates from a first wiring layer to a second wiring layer via the notched section  2   a  so as to communicate from the second wiring layer to a third wiring layer via the notched section  3   a.

TECHNICAL FIELD

The present invention relates to a multi-layer optical fiber sheet inwhich optical fibers can be disposed densely. Also, the presentinvention relates to a method for manufacturing an optical fiber sheetin which optical fibers are disposed on a flexible sheet, and to anoptical fiber sheet.

BACKGROUND ART

In a conventional optical fiber sheet, optical fibers are disposedbetween two flexible resin sheets having the same size as each otherwhich are attached together. Such a conventional optical fiber sheet isusually manufactured by disposing optical fibers on surfaces of sheetson which a pressure sensitive bonding agent (adhesive agent) is applied,and attaching a sheet on which a pressure sensitive bonding agent isapplied thereto. Optical fiber sheet is used mainly for a wiring sectionin an optical fiber in an optical apparatus.

For example, in case in which an extra length part of the optical fiberpath is disposed for an optical fiber sheet, it is limited to bend theoptical fiber. If such an extra length pat to be used for a wiringsection is too long, the optical fiber wiring section is too dense(crowded); thus, there occur direct crosses between the optical fibersin the sheet too often. Therefore, such a direct cross region becomes abulge; thus, there is a disadvantage in that it is difficult to fix thedisposed optical fiber. That is, if so many optical fibers crosses eachother, close contact (adhesion) in both sheets which are disposedvertically tend to be reduced; thus, it may occur that the disposedoptical fibers move undesirably. When the optical fiber is not fixed ina desirable position in the sheet reliably, the optical fibers cannot bedisposed in the sheet accurately so as to be assembled in a device dueto its successive usage for a long period. In some cases, there is aconcern that the optical fiber may be damaged.

Also, a multiple crossings may occur easily in which a plurality ofoptical fibers crosses each other collectively. In such a multiplecrossing region, there is a concern that an unacceptable bending mayoccur on the optical fibers. Furthermore, there is a case in which asheet area must be enlarged so as to prevent the multiple crossings.

Also, in the above conventional optical fiber sheet, when an opticalconnector is attached to the optical fiber which expands from the sheetnear an marginal end of the optical sheet, it is not possible to attachthe optical connector if the optical fiber which is expanded from themarginal end of the sheet is too short. Therefore, predetermined extralength of the optical fiber is necessary so as to attach the opticalconnector near the marginal end of the sheet. Also, for a case in whichthe optical connector is failed to be attached, it is necessary toprepare a greater extra length of the optical fiber so as to cut theoptical fiber to attach the optical fiber again. Therefore, it isnecessary to prepare a predetermined length of optical fiber from amarginal end of the sheet to a rear end of the optical connector. Thus,there is a disadvantage in that it is difficult, or impossible, tomanufacture an optical fiber sheet if the optical fiber has a shortextra length, or if the optical fiber has no extra length.

Also, in an optical fiber sheet, a plurality of optical fibers areusually disposed. That is, only an optical fiber is not disposed in anoptical fiber sheet. When optical connectors are attached to a pluralityof optical fibers respectively near the marginal end of the sheet suchthat a distance from the marginal end of the sheet should be constant,it is necessary to adjust the length of the extra portion of the opticalfiber so as to realize a low skew (that is, to reduce non-uniformdistances from the marginal end of the sheet). In the above conventionalstructure, it is necessary to prepare an area in the optical fiber sheetfor disposing an extra length of the optical fiber so as to adjust theextra length of the optical fiber in addition to a necessary area fordisposing an optical fiber. Therefore, size of the optical fiber sheetmay becomes undesirably large.

Here, in case in which a lot of optical fibers are disposed such thatthe extra length of optical fiber is disposed in the same area as thenecessary wiring area, the wiring condition of the optical fibers becomemore complicated; thus, a multiple crossing in which more than threeoptical fibers cross each other collectively may occur easily.Furthermore, the optical fibers may be bent in an area in which theoptical fibers are crossing each other. If two optical fibers arecrossing, the bending of the optical fibers may be acceptable. However,if more than three optical fibers are crossing, the bending of theoptical fibers may not be in an acceptable range. Furthermore, there isa bulge of the optical fibers in such a crossing area; thus, there is aconcern that the adhesion of the sheet may be insufficient.

In order to solve the above problems, it is necessary to form an areafor disposing an extra length of the optical fiber in addition to anecessary area for disposing the optical fiber by enlarging the sheetarea.

Such an area for disposing an extra length of the optical fiber is notlimited in a case for attaching the optical connector. That is, such anarea for disposing an extra length of the optical fiber is necessary invarious cases in which extra length of the optical fiber is needed.

DISCLOSURE OF INVENTION

The present invention was made in consideration of the aboveconventional problems. A first object of the present invention is toprovide a multi-layer optical fiber sheet in which crossing of theoptical fibers is eliminated or reduced as minimum as possible in awiring plane, the optical fibers are fixed reliably, and an unacceptablebending of the optical fibers due to the multiple crossing of theoptical fibers can be prevented while disposing the optical fibersdensely in a limited area in the sheet.

A second object of the present invention is to provide a method formanufacturing an optical fiber sheet in which it is possible to attachthe optical connector while preparing a sufficient extra length of theoptical fiber and more extra length of the optical fiber, and it ispossible to dispose an extra length of optical fiber in various cases inwhich an extra length of optical fiber is necessary without disposing anunnecessary area for disposing an extra length of optical fiber in alimited area in the sheet.

In order to solve the above problems, in a multi-layer optical fibersheet according to the present invention having multi-layered opticalfiber over a plurality of wiring layers which is formed by attachingmore than three sheets, an interlayer communicating section is formed inat least an intermediate sheet among the sheets, and the optical fiberswhich are disposed in the sheets communicates a region between thewiring layers via the interlayer communicating section.

In the above multi-layer optical fiber sheet, it may be preferable thatthe interlayer communicating section in the sheets which overlapvertically each other do not overlap precisely each other.

In the above multi-layer optical fiber sheet, it may be preferable thata plurality of the optical fibers are disposed such that each opticalfiber is drawn out of the sheets from different region in the sheets.

In the above multi-layer optical fiber sheet, it may be preferable thatthe intermediate sheet is mainly made of a pressure sensitive bondingagent.

In the above multi-layer optical fiber sheet, it may be preferable thatan intermediate layer for fixing optical fibers is disposed betweenoptical fiber sheets which are layered vertically, the optical fibersare disposed on different wiring planes in the intermediate layer, andoptical fiber paths for communicating the different wiring planes areformed in a region between the optical fiber sheets which are layeredvertically.

In the above multi-layer optical fiber sheet, it may be preferable thatthe intermediate layer is a pressure sensitive bonding agent layer.

A method for manufacturing an optical fiber sheet according to thepresent invention comprises the steps for disposing optical fibers on afirst sheet by a desirable pattern, applying a second sheet on the firstsheet so as to have an interlayer communicating section therebetween,attaching an optical connector on a tip of an optical fiber which isdrawn out of the sheets, disposing the optical fiber to which theoptical connector is attached on the second sheet via the interlayercommunicating section, and applying a third sheet on the second sheet.

The above method for manufacturing an optical fiber sheet furthercomprises the steps for disposing an optical fiber tentatively on thesecond sheet such that a predetermined length of the optical fibershould be drawn out of an end margin of the sheet, removing the opticalfiber which is tentatively disposed on the second sheet, attaching anoptical connector on a tip of the removed optical fiber, disposing theoptical fiber on the second sheet again, and applying the third sheet tothe second sheet.

In the above method for manufacturing an optical fiber sheet, it may bepreferable that the optical fiber is drawn out to the interlayercommunicating section.

The above method for manufacturing an optical fiber sheet comprises thesteps for disposing optical fibers on a first sheet by a desirablepattern, applying a second sheet, which is provided with a notchedsection in a region to which the optical fiber is drawn, on the firstsheet, disposing an optical fiber tentatively which expands from thenotched section on the second sheet such that a predetermined length ofthe optical fiber should be drawn out of an end margin of the sheet,removing the optical fiber which is tentatively disposed on the secondsheet, disposing the optical fiber on the second sheet again so as tohave a predetermined extra length of optical fiber after disposing theoptical fiber, and applying the third sheet to the second sheet.

In the above method for manufacturing an optical fiber sheet, it may bepreferable that an intermediate layer for fixing an optical fiber isformed between sheets which are layered vertically, the optical fiberhas different wiring plane in the intermediate layer, optical fiberpaths which communicates the wiring planes a formed inside the sheets,and the optical fiber is disposed on the different wiring plane so as bedrawn out of the sheets to be connected to the connector.

In the above method for manufacturing an optical fiber sheet, it may bepreferable that the intermediate layer is a pressure sensitive bondingagent layer.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1F are views for explaining steps for manufacturing amulti-layer optical fiber sheet according to an embodiment of thepresent invention.

FIG. 2 is a cross section of FIG. 1A structurally viewed in a line A-A.

FIGS. 3A to 3F are views for explaining steps for manufacturing amulti-layer optical fiber sheet according to other embodiment of thepresent invention.

FIG. 4 is a view for explaining a modified example for the embodimentshown in FIG. 3.

FIG. 5 is a plan view of a multi-layer optical fiber sheet according tofurther other embodiment of the present invention.

FIG. 6 is a plan view of a multi-layer optical fiber sheet according tofurther other embodiment of the present invention which corresponds toFIG. 1D showing a manufacturing step.

FIG. 7 is a plan view of a multi-layer optical fiber sheet according tofurther other embodiment of the present invention.

FIGS. 8A to 8F are views for explaining a method for manufacturing anoptical fiber sheet according to an embodiment of the present inventionsuch that an optical fiber sheet should be manufactured in the steps inan order from 8A to 8F.

FIG. 9 is a cross section of FIG. 8F viewed in a line A-A.

FIG. 10 is a cross section of an optical fiber sheet for otherembodiment of the present invention.

FIGS. 11A and 11B show an optical fiber sheet according to further otherembodiment. FIG. 11A is a plan view of the optical fiber sheet beforethe manufacturing steps have not been completed. FIG. 11B is a plan viewof the optical fiber sheet after the manufacturing steps have beencompleted.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferable embodiments for a multi-layer optical fiber sheet, amanufacturing method for an optical fiber sheet, and an optical fibersheet are explained below with reference to drawings. It is understoodthat the present invention is not limited to the embodiments below. Forexample, it is possible to combine each structural members in theembodiments preferably.

Also, in explanations for the embodiments below, it should be understoodthat n-core optical fiber indicates that n pieces of singe core opticalfibers are disposed flatly so as to be formed in an optical fiber.

First Embodiment

A first embodiment of the present invention is explained as follows withreference to FIGS. 1A to 7.

FIGS. 1A to 1F are views for explaining steps for manufacturing amulti-layer optical fiber sheet according to an embodiment of thepresent invention. FIG. 2 is a structurally enlarged cross section ofFIG. 1F structurally viewed in a line A-A so as to show a relationshipof each layer in a manufactured multi-layer optical fiber sheet. In themulti-layer optical fiber sheet shown in the drawing, quite a long extralength of optical fiber which is formed on the optical fiber wiringsection is contained in the optical fiber sheet.

Here, a material for a sheet 1 is explained. A material member for asheet which is used for outermost layers which are on top and the bottomof the sheet is a flexible resin sheet. The material member and thethickness are selected preferably in consideration of Young's modulusaccording to necessary factors such as handling operability,anti-abrasion, rigidity (anti-bending rigidity), and tensile strength.For example, for the material member, a film is used such as polyimide,polyethyleneterefthalate, low density or high density polyethylene,polyprophlene, polyester, nylon 6, nylon 66,ethylene-tetrafluoroethylene copolymer, poly 4-methylpentene,polyvinyllidene chloride, plasticized polyvinylchloride, polyetherestercopolymer, ethylene-vinylacetate copolymer, soft polyurethane.

Here, it is possible to combine any of the sheet material. For example,it is possible to use the same material member as in the top layer andthe bottom layer. Also, it is possible to use different material memberin the top layer from the bottom layer. It may be acceptable if thethickness of the sheet may be the same as in top and bottom sheet. Also,it may be acceptable if the thickness of the sheet may be differentbetween the top sheet and the bottom sheet. Also, a room temperaturepressure sensitive bonding agent (adhesive agent) including a rubber oracryl is applied on a surface of the sheet member so as to attachtogether. Also, although an optical fiber which is disposed on the sheetis not limited particularly, so called a UV (ultraviolet) line (diameter250 μm) which is formed by a UV resin coating on a bare fiber, or asilicon wire on which a silicon resin is coated is usually used. Also,it is possible to use an optical fiber cord of which optical fiber coreand a protecting coat are reinforced, an optical fiber tape cord ofwhich optical fiber tape core and a protecting coat are reinforced, anda carbon coat fiber according to necessity. Also, in the embodiments ofthe present invention, explanation is not limited to a case in which afirst sheet is the bottom layer and a second sheet is the top layer.More importantly, an opposite structure is acceptable. If there are morethan three sheets, it is acceptable if a sheet which is not disposed onthe outermost layer may be the first sheet.

First, an optical fiber 5 is disposed on a first sheet 1 (bottom layer)as shown in FIG. 1A. A pressure sensitive bonding agent is applied on anupper surface of the sheet 1, and an optical fiber 5 is disposed thereonat a desirable pattern so as to be pushed by a slight pushing force. Theoptical fiber 5 adheres to the sheet; thus such a wiring condition ismaintained. Here, the desirable pattern indicates a wiring condition inwhich overlapping optical fibers are prevented as much as possible so asto realize a sufficient curvature such that a bending loss of the lightmay be restricted in an acceptable range. For example, for a desirablepattern, it is possible to mention to a wavy shape, only a curved shapesuch as an ellipse or a circle, otherwise a combination of these shapeswith a linear section. If the sheet 2 and the bottom sheet 1 iscompressed to be attach together, they are hardly removed from eachother; thus, position of an optical fiber which is disposed between thesheets 1 and 2 is fixed by an adhesive member.

The above feature such as thickness of the sheet, a compressingoperation for the sheet, and a desirable pattern can be employedpreferably in the rest of the embodiments of the present invention.

Here, in FIG. 1A, it is understood that a region which is indicated byan arrow “a” is used for inputting purpose. Also, as understood from thedrawing, an outputting region for the optical fiber 5 is omitted in thedrawing.

Next, as shown in FIG. 1B, a second sheet 2 in which, for example, arectangular notched section 2 a is formed as an interlayer communicatingsection is applied in a right-bottom region in the drawing for a vieweron the first wired sheet 1. This sheet 2 is an interlayer sheet in whichthick pressure sensitive bonding agent (adhesive member) is disposedbetween dual-surfaced removal papers (separators). Here, a removal paperis removed so as to expose an adhesive layer so as to be compressed in apredetermined position of the sheet 1 such that the optical fiber issandwiched therebetween. After the sheet 2 is compressed to be attachedwith the sheet 1, the other removal paper on the sheet 2 is removed soas to expose the pressure sensitive bonding agent (adhesive member).That is, the sheet 2 is formed only by a pressure sensitive bondingagent layer.

Next, as shown in FIG. 1C, an outputting region of the optical fiber 5which is disposed on the first sheet 1 is introduced on the second sheet2 via the notched section 2 a so as not to expand over the sheet; thus,the optical fiber 5 is disposed on the second sheet 2. Here, in FIG. 1C,wiring section in a first wiring layer (a region which is indicated by abroken line in FIG. 1B) is omitted.

Next, as shown in FIG. 1D, a sheet 3 having a rectangular notchedsection 3 a formed in a upper-left region for the viewer in the drawingis applied on the wired second sheet 2 such that the rectangular notchedsection 3 a should be disposed in different position (in differentcorner in this embodiment) from a position of the notched section formedon the second sheet 2. The sheet 3 is also an intermediate layer whichhas a similar structure with the second sheet 2. Here, an order forapplying the sheets is similar to the above case; thus, explanation isomitted.

Next, as shown in FIG. 1E, as similar to the previous step, anoutputting region of the optical fiber 5 which is disposed on the secondsheet 2 is introduced on the third sheet 3 via the notched section 3 aso as to be disposed on the third sheet 3. Here, in FIG. 1E, wiringsection in a second wiring layer (a region which is indicated by abroken line in FIG. 1D) is omitted.

Next, as shown FIG. 1F, a top fourth sheet 4 which has the same shape asthe bottom sheet 1 is applied on the wired third sheet 3. The pressuresensitive bonding agent is applied on a surface of the sheet 4. By doingthis, a multi-layer optical fiber sheet 6 is formed in which opticalfibers are disposed over three wiring layers (wiring planes).

As an entire result, an intermediate layer which is formed by aplurality of layers of pressure sensitive bonding agent is formedbetween the material members for the sheets which are layeredvertically, and optical fibers are disposed so as to be embedded on aplurality of different planes (wiring planes) in the intermediatelayers.

In such an intermediate layer, there is a case in which it is difficultto separate the layers because the layers are unitarily formed by acompressing operation; thus, a border between the adhesive layers is notclear, or there is no border betwee the adhesive layers. However, suchan intermediate layer can be a plurality of wiring layers (multi-layer)because there are a plurality of wiring planes in the optical fiberviewed in a cross section of the optical fiber sheet. Therefore, such anintermediate layer can be in a range of the present invention. That is,in the present invention, an intermediate layer for fixing the opticalfiber is formed between the optical fiber sheets which are layeredvertically, and the optical fiber has different wiring planes in theintermediate layers. Additionally, optical fiber paths whichcommunicates among the wiring planes (layers) are formed inside theoptical fiber sheet. Although the intermediate layer is formed by anacrylic pressure sensitive bonding agent (adhesive agent), it is notnecessary that the intermediate layer should maintain an adhesivecharacteristics after it is applied on the sheet. That is, an object ofthe intermediate layer is to maintain a wiring condition of the disposedoptical fibers flexibly; therefore, a material for the intermediatelayer is not limited to a material member which has a common adhesiveagent. It is in a range of the present invention if a material memberwhich has an aging characteristic so as to become a rubber elastomerafter being attached or a material member which decomposes according toa thermal history is used for the intermediate layer.

Here, in the above explanations, a sheet which is formed by disposing athick pressure sensitive bonding agent (adhesive agent) betweendouble-surfaced removal papers is used for each intermediate layer.However, it is possible to use a sheet in which a pressure sensitivebonding agent is applied on both sides of the material members for thesheet which is similar to the outermost layer as a part of theintermediate sheet as an object for enhancing a rigidity of the sheet.Furthermore, the intermediate layer may be a composite in which severalsheets having only an adhesive agent and sheets having a material memberare combined.

Inside the above multi-layer optical fiber sheet 6, quite a long extralength of the optical fiber 5 is contained. Here, the optical fiber 5 isdisposed over three wiring layers (wiring planes). Therefore, although asheet area is limited, the optical fibers 5 which are disposed in eachwiring layer are not so dense (crowded). Therefore, the optical fibersdo not cross each other in each wiring layer. Otherwise, only a fewoptical fibers cross each other even if there is such optical fiberswhich are crossing each other. The neighboring sheets which are layeredvertically are contacting each other closely; thus, the optical fibersare fixed reliably; thus, there is not a concern that the optical fibersmove in the sheet. Therefore, there is not a concern that the opticalfibers may be disposed inaccurately on the sheet such that the opticalfibers may be damaged when the optical fiber sheet is assembled in adevice.

Also, it is possible to prevent a multiple crossing region in which aplurality of optical fibers cross collectively. Thus, there is not aproblem in that there may be an unacceptable range of bending in theoptical fibers in such a multiple crossing region. Nevertheless eachoptical fiber is drawn from a region near the sheet in the presentembodiment, positions from which each optical fiber is drawn thereout isdifferent when viewed from a cross sectional direction of the sheet.Therefore, there is not a multiple crossing between the optical fibers.Otherwise, even if there is a multiple crossing between the opticalfibers, it is possible to design a wiring shape in which there may beless number of multiple crossings.

Although the above embodiment employs a four-layer structure in whichtwo intermediate layers are used, it is possible to select the quantityof the intermediate layer and total layers preferably. A order fordisposing wirings is the same as in each example; therefore,explanations for such an order is omitted.

Furthermore, in the above embodiment, an example for a case in which anoptical fiber is disposed in an multi-layer optical fiber sheet isshown. However, in a case in which a plurality of optical fibers aredisposed, density of the wirings is conspicuous; therefore, the presentinvention is particularly effective for a case in which a plurality ofoptical fibers are disposed. FIGS. 3A to 3F are showing manufacturingsteps for a multi-layer optical fiber sheet 6A in which two single coreoptical fibers (or a single two-core optical fiber tape) are disposed.

In the manufacturing steps for the multi-layer optical fiber sheet 6A,the steps shown in FIGS. 3A to 3D correspond to FIGS. 1A to 1D exceptthat two optical fibers are used (two optical fibers are indicated byreference numerals 5 and 5′). In FIG. 3E, an optical fiber is introducedonto a third sheet 3 via a notched section 3 a so as to be disposed onthe third sheet 3 as similar to FIGS. 1A to 1F. In contrast, the otheroptical fiber 5′ is not disposed on the sheet 3. Instead, the opticalfiber 5′ is drawn out of the sheet. Consequently, a fourth sheet 4 isapplied thereon. Thus, a multi-layer optical fiber sheet 6A in which twooptical fibers 5 and 5′ are disposed over three layers is manufactured.

Also, although it is not explained later, in a case in which n-coreoptical fiber tape (n is an integer) is used, the above wiringdisposition is performed by cutting the n-core optical fiber tape into asingle core optica fiber at a preferable position on the sheet; thus,the optical fiber which is cut is drawn out of the sheet similar to theabove explanation.

In the above example, although the other optical fiber 5′ is drawn outof the sheet from the notched section 3 a as shown in FIGS. 3D and 3E,it is possible to select the region for drawing out the optical fiberpreferably. For example, as shown in FIG. 4, the optical fiber 5′ may bedrawn out of the sheet horizontally from, for example, a left member ofthe sheet. Here, it is possible to draw the optical fiber from a commonmember of the sheet (in the same direction) such that an exit positionof the optical fiber is shifted from an exit position on the otherlayer.

Also, in case in which, for example, four optical fibers (or a four-coreoptical fiber) are disposed, it is possible to draw the optical fibersfrom four directions on the sheet.

By doing this, in case in which it is necessary to draw a plurality ofdisposed optical fibers in plural directions, it is possible to draw theoptical fibers from plural directions easily without a multiplecrossing. That is, it is possible to draw the optical fibers from pluralregions.

In the above embodiment, a notched section is formed on the sheet for alinear interlayer communicating section. More importantly, it isacceptable if a hole 3 b is formed for an interlayer communicatingsection as shown in FIG. 6. FIG. 6 corresponds to a step shown in FIG.1D among manufacturing steps shown in FIGS. 1A to 1F. Here, anoutputting section of the optical fiber 5 which is disposed on thesecond sheet 2 is introduced onto the third sheet 3 via the hole 3 b soas to be disposed on the third sheet 3.

Here, if either one of the neighboring sheets is smaller than the othersheet, that is, if a longitudinal width and a latitudinal width arenarrower, it is possible to form a non-conforming section.

Second Embodiment

It is possible to form a following structure for a second embodiment ofthe present invention.

{circle around (1)} Shape of the notched section for an interlayercommunicating section or a hole are not limited in a rectangular; thus,any shape is acceptable.

That is, it is important that the shape of the intermediate sheet shouldnot conform with the shape of the neighboring sheet such as a sheettherebeneath. Such a non-conforming section forms an interlayercommunicating section. For example, when a first intermediate sheethaving a narrower width than that in the sheet 1 of the presentembodiment is used, a region in which the shape of both sheets does notcoincide forms an interlayer communicating section.

{circle around (2)} Also, in a case in which a first intermediate sheet2 having narrower longitudinal width and narrower latitudinal width thanthose in the sheet 1 is used, a non-conforming section forms aninterlayer communicating section.

{circle around (3)} In a case in which a sheet 1 is formed like a combsuch that a plurality of drawn sections 1 a are formed as shown in FIG.7, if a shape a first intermediate sheet 2 is different (a rectangularshape in an example shown in drawing) from a shape of the sheet 1 asshown in the drawing, an interlayer communicating section is formedsimilarly.{circle around (4)} It is sufficient if an interlayer communicationsection is formed in the intermediate sheet; thus, it is certain thatthe intermediate layer should not be formed on the bottom sheet and onthe top sheet necessarily. However, the present invention does noteliminate a case in which notched section and a hole for other objectcan be formed on the bottom sheet and on the top sheet.{circle around (5)} A multi-core optical fiber is introduced from acertain end so as to be branched in a multi-core manner inside the sheetso as further to branch them into a single-core optical fibers or a lessmulti-core optical fibers. For example, it is possible to mention a casein which an eight-core optical fiber tape is inputted so as to be cutinto four pieces of two-core optical fibers (tapes). Alternatively, itis possible to mention a case in which an eight-core optical fiber tapeis inputted so as to be cut into eight pieces of single-core opticalfibers. It is acceptable if a divided optical fiber may be introduced toan exit. It is also acceptable if the optical fiber may be separated inan intermediate sheet so as to be branched in a plurality of exits.{circle around (6)} Regarding a method for disposing an extra length ofthe optical fiber, there is a case in which the optical fibers aredisposed so as not to cross and overlap vertically in a layer (wiringplane). Also, there is a case in which the optical fibers are disposedso as to cross and overlap vertically in a layer. The wiring conditionis determined according to a specification of a product desirably.{circle around (7)} It is sufficient as long as a position and a shapeof the interlayer communicating sections do not coincide and overlapcompletely. The present invention does not eliminate a case in which aposition and a shape of the interlayer communicating sections maycoincide partly.

Third Embodiment

A third embodiment of the present invention is explained with referenceto FIGS. 8A to 8F, 9, 10, 4, and 5. A portion of the optical fiber whichis drawn out of the sheet is covered by a reinforcing tube which isprovided with a reinforcing texture layer. In particular, when anoptical connector is attached, it is necessary to cover the opticalfiber by the reinforcing tube in advance. For an optical connector(optical ferrule), a common single-core SC optical ferrule can be used.Also, a multi-core MT optical ferrule can be used preferably.

FIGS. 8A to 8F are views for explaining a method for manufacturing anoptical fiber sheet of the present invention. FIG. 9 is an enlargedcross section of manufactured optical fiber sheet FIG. 8C viewed in aline A-A. First, as shown in FIG. 8A, an optical fiber 12 is disposed ona flexible resin sheet (a first sheet) 11 on which a pressure sensitivebonding agent is applied. In the drawing, an example for a case in whichan optical fiber 12 in which an optical fiber connecter 13 is attachedto an inputting section is disposed on the sheet, and an opticalconnector 14 (see FIGS. 8D to 8F) is attached to an outputting sectionis shown.

Here, a material for a sheet 11 is explained. A material member for asheet which is used for outermost layers which are on top and the bottomof the sheet is a flexible resin sheet. The material member and thethickness are selected preferably in consideration of Young's modulusaccording to necessary factors such as handling operability,anti-abrasion, rigidity (anti-bending rigidity), and tensile strength.For example, for the material member, a film is used such as polyimide,polyethyleneterefthalate, low density or high density polyethylene,polyprophlene, polyester, nylon 6, nylon 66,ethylene-tetrafluoroethylene copolymer, poly 4-methylpentene,polyvinyllidene chloride, plasticized polyvinylchloride, polyetherestercopolymer, ethylene-vinylacetate copolymer, soft polyurethane.

Also, it is possible to combine any of the sheet material. For example,it is possible to use the same material member as in the top layer andthe bottom layer. Also, it is possible to use different material memberin the top layer from the bottom layer.

Also, a room temperature pressure sensitive bonding agent (adhesiveagent) including a rubber or acryl is applied on a surface of the sheetmember so as to attach together. Also, although an optical fiber whichis disposed on the sheet is not limited particularly, so called a UV(ultraviolet) line (diameter 250 μm) which is formed by a UV resincoating on a bare fiber, or a silicon wire on which a silicon resin iscoated is usually used. Also, it is possible to use an optical fibercord of which optical fiber core and a protecting coat are reinforced,an optical fiber tape cord of which optical fiber tape core and aprotecting coat are reinforced, and a carbon coat fiber according tonecessity.

Next, as shown in FIG. 8B, a second sheet 15 which is supposed to be anintermediate layer having, for example, a rectanbular notched section 15a for an interlayer communicating section is attached in a right-topregion of the sheet 11 for a viewer on the first wired sheet 11. Thesheet 15 is formed by disposing a thick pressure sensitive bonding agent(adhesive agent) layer between a double-surfaced removal papers suchthat an adhesive layer is exposed by removing a removal paper so as tobe compressed to be attached in a predetermined position on the sheet 11so as to dispose the wired optical fiber 12 therebetween. After thesheet 15 is compressed to the sheet 11 therebeneath, the other removalpaper is removed so as to expose the pressure sensitive bonding agent(adhesive agent). That is, the sheet 15 is formed only by a layer of thepressure sensitive bonding agent.

Next, as indicated by a line in FIG. 8C, the optical fiber 12 is bentdownwardly in the drawing in the notched section 15 a so as to disposean extra length portion of the optical fiber 12 tentatively on theattached sheet 15. The extra length part which is tentatively disposedto roll around on the sheet 15 is indicated by reference numeral 12′. Insuch a tentative disposition, when the extra length portion of theoptical fiber 12 which is tentatively disposed is compressed on thesheet 15 by a slight force, it is possible to remove easily therefromlater. Consequently, the drawn part of the optical fiber is cut suchthat a predetermined length L₁ is drawn from a marginal end of thesheet. The drawn length L₁ corresponds to a final position in which theoptical connector 14 is attached as shown in FIG. 8E.

The attaching operation for the optical connector under the abovecondition is not satisfactory; next, the extra length part 12′ which istentatively disposed is removed so as to draw the optical fiber 12straightly so as to attach the optical connector 14 in a tip of theoptical fiber 12 as shown in FIG. 8D. In such a case, an extra lengthpart 12 a to which the optical connector 14 is supposed to be attachedsuch as an extra length section L₂ of the optical fiber 12 issufficiently long; it is easy to attach the optical connector 14.

Next, as shown in FIG. 8E, the extra length section (also indicated byreference numeral 12 a) is disposed on a surface of the sheet 15. Ifsuch an extra length section for the optical connector 14 is disposedsuccessfully for the first time, the extra length section is disposed inthe same pattern as the tentative disposition pattern shown in FIG. 8C.By doing this, it is possible to attach the optical connector 14according to a designed distance L₃ (or L₁) from the marginal end of thesheet correctly. Therefore, it is possible to manufacture an opticalfiber sheet having a short extra length section (a distance L₃ from themarginal end of the sheet to the rear end of the optical connector isshort) easily. Also, it is possible to manufacture an optical fibersheet having no extra length section (a distance L₃ is zero) easily.

In a case in which the optical connector 14 cannot be attachedsuccessfully in a manufacturing step shown in FIG. 8D because asufficient optical performance cannot be realized or the optical fiberis broken, it is possible to cut the tip of the optical fiber 2 so as toattach the optical connector 4 again because there is a sufficient extralength to be attached. Here, if the extra length section 12 a isdisposed on a surface of the sheet 15, the extra length section 12 isslightly different from the tentative disposition pattern shown in FIG.8C because the extra length section 12 a is slightly short. Although thedisposing operation should be performed in consideration of the abovedifference, it should be noted that there may be a case in which theremay not be a region for rolling the optical fiber in the sheet.

Next, as shown in FIG. 8F, a sheet 16 (third sheet) on which surface apressure sensitive bonding agent is applied having an area for coveringthe notched section 15 a is attached on the sheet 15 in which an extralength section is formed. By doing this, a two-layer structure opticalfiber sheet 17 is manufactured in which an optical fiber for theoutputting use is disposed on a layer (wiring plane) which is differentfrom the optical fiber for the inputting use and the sheet 15.

In the above explanation, although a case in which only an optical fiber12 is disposed in the optical fiber sheet 17 is explained, a lot ofoptical fibers are disposed usually. Embodiments shown in FIGS. 10 and 4relates to a optical fiber sheet in which, for example, four opticalfibers 12 are disposed. Here, an inputting section is an optical fibertape in which four pieces of single-core optical fibers 12 are bundled.Additionally, the optical fiber tape is attached to a four-core opticalfiber connector 13A so as to be disposed on the optical fiber sheet 1.The disposed optical fiber tape is cut into a single-core optical fiber12 a in the sheet so as to be drawn out of the sheet. An opticalconnector for a single-core optical fiber is attached on a tip of thesingle-core optical fiber 12 a.

Here, any desirable number of optical fibers can be disposed. Forexample, it is acceptable if the inputting section is a four-coreoptical fiber tape so as to be cut into optical fibers having lessnumber of cores such as a single-core optical fiber tape or a two-coreoptical fiber tape.

In this case, the optical fiber has a dimensional two-layer structure;therefore, even if the extra length section (upper wiring layer) isdisposed so as to overlap the necessary wiring section (lower wiringlayer), the optical fibers are not disposed crowdedly. Thus, it ispossible to avoid the multiple crossing of the optical fibers easily.Therefore, it is not necessary to form an extra area for containing suchan extra length section by enlarging the sheet area.

Consequently, it is possible to obtain a sufficient extra length section12 a; therefore, it is possible to attach the optical connector 14 by anaccurate distance from the marginal end of the sheet. Furthermore, it ispossible to realize a low skew (reduce uneven distance from the marginalend of the sheet). By doing this, it is not necessary to form an extralength area in addition to a necessary wiring area for the optical fiberso as to realize a low skew.

Here, FIG. 10 corresponds to a manufacturing step shown in FIG. 8E inwhich an optical fiber sheet 17A is manufactured by attaching a thirdsheet 16 on the sheet 15 in which an extra length section 12 a of theoptical fiber is disposed as shown in FIG. 4.

Here, in the embodiments shown in FIGS. 10 and 4, the notched section 15a which is supposed to be formed on the sheet 15 for disposing an extralength section is disposed in a marginal end section in an outputtingsection of the optical fiber sheet. Here, it is possible to dispose thenotched section 15 a′ in an inputting section shown in FIG. 5 whichshows a corresponding manufacturing step s to that of FIG. 8F. That is,it is possible to form a notched section in the marginal end section ineither one of the sheet of the optical fiber which is disposed on theoptical fiber sheet. Although it is not shown in the drawingparticularly, it is possible to form on both the inputting section andthe outputting section.

Although the above embodiment employs two-layer structure, the presentinvention can be applied to a case in which more than three-layerstructure is employed. As shown in FIGS. 11A and 11B, when four opticalfibers (quantity of core can be determined preferably whether to usefour pieces of single-core optical fibers or a four-core optical fiber)is disposed, four optical fibers 12 which are disposed on the firstsheet 11 are drawn out from the notched section 15 a formed on thesecond sheet 15 which is supposed to be an intermediate layer so as toform an interlayer communicating section; thus, the optical fibers aredisposed on the second sheet 15. In such a case, after two opticalfibers 12 are removed, optical connector is attached so as to disposethe optical fiber again (see FIG. 11A).

Furthermore, the rest of two optical fibers 12 are drawn out from thenotched section 16′a which is formed on the third sheet 16′ which issupposed to be an intermediate layer so as to be attached on the secondsheet 15 so as to be disposed on the third sheet 16′. In such a case,after the tentative disposed wiring is removed, the optical connector isattached according to the above method so as to dispose the opticalfiber again. Next, a fourth sheet 20 is attached thereon (see FIG. 11B).

Here, in the above case, it is acceptable if the extra length forattaching the optical connector 14 to the two optical fibers 12 on thesecond sheet 15 may be the same the extra length for attaching theoptical connector 14 to the optical fibers 12 on the third sheet 16′.Alternatively, the extra length for attaching the optical connector 14to the two optical fibers 12 on the second sheet 15 may be differentfrom the extra length for attaching the optical connector 14 to theoptical fibers 12 on the third sheet 16′.

Also, in the above embodiments, there may be a case in which it isdifficult to see a border between the sheets or layered sheets mayexternally look as if they are unitarily formed because a plurality ofintermediate layers are made of adhesive layers. The present inventionincludes such a case because wiring planes for the optical fibers aredifferent. It is difficult to separate such interlayers which areusually unitarily compressed. Otherwise, the border between the adhesivelayers are unclear. Furthermore, there may be a case in which there isno border between the adhesive layers. In such a case, there are aplurality of wiring planes for the optical fibers when viewed from across section of the optical fiber sheet; it is possible to understandthat such a structure may be a plurality of wiring layers(multi-layers). Therefore, such a structure can be included in atechnical scope of the present invention.

That is, in the present invention, an intermediate layer for fixing anoptical fiber between optical fiber sheets which are layered verticallyis disposed, and the optical fiber has different wiring planes in theintermediate layer. Consequently, the optical fiber paths whichcommunicate among the wiring planes (layers) are formed inside theoptical fiber sheet. Although the intermediate layer is an acrylicpressure sensitive bonding agent (adhesive agent) layer, it is notnecessary to maintain such adhesion after the sheet is attached. Thatis, object of the intermediate layer is to maintain a wiring conditionof the disposed optical fibers flexibly; therefore, a material for theintermediate layer is not limited to a material member which has acommon adhesive agent. It is in a range of the present invention if amaterial member which has an aging characteristic so as to become arubber elastomer after being attached or a material member whichdecomposes according to a thermal history is used for the intermediatelayer.

Here, in the above explanations, an intermediate sheet which is formedby disposing a thick pressure sensitive bonding agent (adhesive agent)between double-surfaced removal papers is used for each intermediatelayer. However, it is possible to use a sheet in which a pressuresensitive bonding agent is applied on both sides of the material membersfor the sheet which is similar to the outermost layer as a part of theintermediate sheet as an object for enhancing a rigidity of the sheet.Furthermore, the intermediate layer may be a composite in which severalsheets having only an adhesive agent and sheets having a material memberare combined.

Fourth Embodiment

It is possible to employ a following structure as a fourth embodiment ofthe present invention below.

{circle around (1)} Interlayer communicating section is a general termfor a section which communicates between the wiring planes. Therefore,the shape and the position of the interlayer communicating section canbe determined desirably. In a sheet having a narrower width than theshape of the hole or the width in the other sheet, it is possible toform an interlayer communicating section in such a narrow section. Also,it is sufficient if the position and the shape of the interlayercommunicating section may coincide completely. That is, it is acceptableeven if a part of the position and the shape of the interlayercommunicating section may overlap.{circle around (2)} It is not limited whether or not the optical fibermust be drawn out from a member of the sheet. The present invention canbe applied to a case in which the optical fiber may be drawn out from aplurality of members of the sheet (from different exits).

Furthermore, there is a case not only in that the optical fiber is drawnout from the notched section but also in that the optical fiber is drawnout of the sheet from the other section.

{circle around (3)} The present invention can be employed to a case inwhich an optical fiber which is provided with an optical connector andan optical fiber which is not provided with an optical connector areused together.

{circle around (4)} A object of the tentative disposing step for theoptical fibers on the intermediate layer is to enhance an workingoperability for adjusting the extra length of the optical fibers whichare drawn out of the sheet. Therefore, it is possible to attach theoptical connector by cutting the optical fiber not via the tentativedisposing operation, and after that, it is possible to dispose theoptical fibers on the sheet finally.{circle around (5)} The present invention can be employed for forming apart of layers in a multi-layer wiring structure. That is, it does notmean that the first sheet should be limited either one of the sheetswhich are layered vertically. It should be understood that the firstsheet indicates either one of a plurality of sheets. That is, in thepresent invention, a term such as n_(th) sheet (n is an integer) is usedfor indicating a relative position in the disposed wiring section.

INDUSTRIAL APPLICABILITY

According to the present invention, when an multi-layer optical fibersheet is formed, an interlayer communicating section such as a notchedsection or a hole is formed on the sheet; thus, the optical fibercommunicates to a region between the wiring planes via the interlayercommunicating section. Therefore, there are less dense optical fibers ineach wiring planes; thus, the sheets which are neighboring verticallycontact sufficiently closely; thus, the optical fibers are fixedreliably. Therefore, it is possible to reduce a necessary sheet area.Thus, there is no concern in that the optical fiber is disposed in anundesirable position when assembled in the device and there occurs amicrobent which damages the optical fiber.

Also, it is possible to prevent a multiple crossing section in which aplurality of optical fibers cross each other collectively fromoccurring; therefore, there is no problem in that an insufficientcontact in such a multiple crossing section or a bending of the opticalfiber in an unacceptable range may occur.

Also, when it is necessary to draw a plurality of disposed opticalfibers into a plurality of directions, it is possible to draw theoptical fibers in a plurality of directions without causing a multiplecrossing.

Also, according to a method for manufacturing an optical fiber sheet ofthe present invention, optical fibers are disposed so as to form atleast a two-layer structure in an optical fiber sheet in which opticalfibers are drawn out from an interlayer communicating section which isformed in the intermediate sheet in a three-layered sheets apart fromthe sheets. Therefore, by disposing the optical fibers tentatively ordisposing the optical fibers again, it is possible to obtain asufficient extra length section or more extra length section forre-disposition in the optical fibers which are supposed to be disposed,for example, when optical fibers are attached to the optical fiber whichexpands from the sheet near the marginal end of the sheet. Therefore, itis possible to attach the optical connectors to the optical fibers whichexpand from the sheet near the marginal end of the sheet easily. Also,it is possible to attach optical connectors having a short extra lengthsection of the optical fiber which expands from the marginal end of thesheet. Also, it is possible to attach optical connectors having no extralength section of the optical fiber.

Also, the disposed optical fibers have at least a two-layer wiringplanes when the optical connectors are attached to a plurality of theoptical fibers near the marginal end of the sheet. Therefore, it ispossible to avoid a multiple crossing of the optical fibers easily inwhich the optical fibers are not crowded even if the extra lengthsection is disposed so as to overlap the necessary wiring section.Therefore, it is not necessary to form a surplus area for the are forcontaining the extra length section.

Also, it is possible to obtain a sufficient extra length section in eachoptical fiber; it is possible to attach the optical connector easilysuch that a distance from the marginal section of the sheet may beadjusted constantly and accurately. Therefore, it is possible to realizea low skew in which an unevenness of the position of the opticalconnectors is satisfactorily small.

Furthermore, if the optical connectors cannot be attached to the eitherone of the optical fibers successfully, and it is necessary to cut thefailed connection and attach new optical connectors again for attachingthe optical connectors to a plurality of optical fibers, it is possibleto adjust the length of the expanded optical fibers in a predeterminedlength by adjusting the extra length section (curvature) of the opticalfiber on the sheet.

1. A method for manufacturing an optical fiber sheet comprising thesteps for: disposing optical fibers on a first sheet by a desirablepattern; applying a second sheet on the first sheet so as to have aninterlayer communicating section therebetween; attaching an opticalconnector on a tip of an optical fiber which is drawn out of the sheets;disposing the optical fiber to which the optical connector is attachedon the second sheet via the interlayer communicating section; andapplying a third sheet on the second sheet.
 2. A method formanufacturing an optical fiber sheet according to claim 1 furthercomprising the steps for: disposing an optical fiber tentatively on thesecond sheet such that a predetermined length of the optical fibershould be drawn out of an end margin of the sheet; removing the opticalfiber which is tentatively disposed on the second sheet; attaching anoptical connector on a tip of the removed optical fiber; disposing theoptical fiber on the second sheet again; and applying the third sheet tothe second sheet.
 3. A method for manufacturing an optical fiber sheetaccording to claims 1 or 2 wherein the optical fiber is drawn out to theinterlayer communicating section.
 4. A method for manufacturing anoptical fiber sheet comprising the steps for: disposing optical fiberson a first sheet by a desirable pattern; applying a second sheet, whichis provided with a notched section in a region to which the opticalfiber is drawn, on the first sheet; disposing an optical fibertentatively which expands from the notched section on the second sheetsuch that a predetermined length of the optical fiber should be drawnout of an end margin of the sheet; removing the optical fiber which istentatively disposed on the second sheet; disposing the optical fiber onthe second sheet again so as to have a predetermined extra length ofoptical fiber after disposing the optical fiber; and applying the thirdsheet to the second sheet.